It's Not Easy Keeping Up With a Turtle; Satellite Tracking Is Used to Study a Threatened Species

By TINA KELLEY

Published: July 14, 2005

Gylla MacGregor consulted her Global Positioning System device, laying it on a rock near her somewhat elusive prey. In four hours, the animal had moved all of 396 feet as the crow flies. But it does not fly like a crow. It is a wood turtle, and it had probably lumbered up the stream bed, into a miniature forest of skunk cabbage, most likely covering at least 500 feet.

Ms. MacGregor, an executive assistant with the New Jersey Audubon Society, has used radio telemetry to track four of the turtles known to use the property, somewhere in New Jersey. The number of turtles is dwindling in New Jersey, and Audubon officials do not want to disclose the refuge's location for fear of attracting collectors. It is illegal to collect wood turtles or to sell them as pets.

Ms. MacGregor had glued radio transmitters on the turtles, using plumber's epoxy, because it works in damp conditions. She had attached a bit of guitar string to the transmitter, to act as an antenna.

About every other day Ms. MacGregor walks through the woods, pointing an antenna at the ground, moving it a foot a second in an arc until it beeps louder, narrowing in on Turtle 1 and Turtle 2. ''The beep changes,'' she said. ''It gets almost a little twangy when I'm pointing it right at the turtle.'' As she got closer and the beep got louder, she turned down the volume to gauge the distance to the turtles better.

This is the first year Audubon has studied the turtles in the refuge, in the hope of learning more about the animal, the dangers it faces, the habitat it needs and the best ways to protect it.

''The best data you get is long-term studies of the same individuals, unless you have a whole lot of individuals,'' Ms. MacGregor said. The property is home to 14 wood turtles and 4 box turtles.

The stakes are high in New Jersey, where the wood turtle is on the threatened species list, mostly because the habitat it requires, clean streams or rivers with access to undisturbed uplands, is itself becoming rare. The turtle is in decline across much of its habitat, which includes the Northeast and the Great Lakes region, according to the herpetology center at Indiana University-Purdue University in Fort Wayne.

New Jersey has recorded only 600 wood turtle sightings, and though no exact figures have been collected, their numbers appear to be decreasing, said Brian Zarate , an assistant biologist with the fish and wildlife division of the Department of Environmental Protection.

The wood turtle needs clean water to hibernate near, he said. ''When you start impacting water quality and separating stream corridors and building into uplands, that's when the problem began for turtles,'' he said. ''As urbanization and general sprawl increases, they get pushed back more into remaining rural areas.''

Habitat fragmentation hurts the turtles when they try to move from one small patch of suitable land to another and end up smashed by a car or attacked by a dog or other predators, said Mike Anderson, a program director for the New Jersey Audubon Society. ''Foxes, raccoons, rats, possums -- what we call urban rodents -- remove cover from the turtles, making the young and adults easier to see,'' he said. ''They're easier targets for predators.'' The rising number of deer in the state also probably contributes to reducing the turtles' woodland cover.

State wildlife officials are interested in hearing about wood turtle sightings to get a better handle on their numbers and where they are. Mr. Zarate encouraged people to call (908) 735-8975 to report sightings.

The wood turtle survives on berries, mushrooms, snails, slugs and earthworms, Ms. MacGregor said. It is known to estivate, or go into a dormant state during hot weather, and it also has been observed ''earthworm stomping,'' a way of fishing for earthworms by hitting the ground with its foreleg and bottom shell, causing vibrations that attract earthworms to the surface. It has been seen consuming up to 2.4 worms per hour, according to one study.

Meanwhile, back in the woods, Ms. MacGregor discovered Turtle 2 under a pile of debris on a stream bank, not far from Turtle 1, who is 13, judging by the rings on each scute, or section, of her shell. Turtle 1 likes to move into an upland field for five days at a time, then back down to the stream.

''I'm glad that she's moving beyond that,'' Ms. MacGregor said. ''Hopefully she and other females will lead us to more, and to males.'' She and Mr. Anderson hope to find where they hibernate, often in clusters, to get a better sense of the size of the population here.

Ms. MacGregor has enjoyed how the work takes her away from human surroundings, wandering low among the barberry bushes, for several hours a day.

''I like being able to get into their world, and what they do on a daily basis,'' she said. ''Tracking is fascinating because you go through the habitat they go through, with a totally different perspective. You get a huge appreciation for what something else goes through on a daily basis.''

Photos: A wood turtle being monitored by Gylla MacGregor of the New Jersey Audubon Society. A bit of guitar string acts as an antenna for the turtle's transmitter.; Gylla MacGregor using a radio receiver and an antenna in an area where the turtles are likely to be foraging for food. (Photographs by Joyce Dopkeen/The New York Times)